Rail is an important method of transporting goods and people to and from populated areas. Since rail lines often intersect with road ways or pedestrian crossings, collisions between trains and other traffic often occur. Preferably, rail lines are separated from pedestrian or automobile traffic by overpasses. Not all crossings have sufficient traffic to justify the expense of building an overpass, and in many cases where expense is not an issue, the construction of an overpass is not practical. Where no overpass is possible, the rail lines must cross over the road or pedestrian walk way. To ensure collisions are avoided at rail crossings, rail transport companies often install signal devices designed to warn motorists of the rail crossing. In areas where there is significant rail traffic, these rail crossings may be engineered to autonmatically activate flashing lights, closing gates or auditory alarms when trains approach the crossing.
Automated rail crossings generally consist of a sensor coupled to a control device which is in turned coupled to a signal. The control devices are generally straight forward devices designed to activate the signal as soon as the train reaches the sensor. The sensor is generally positioned several meters away from the crossing thereby ensuring that the signal will be activated before the train reaches the crossing. It is critically important that the signal is activated well before the train enters the crossing so that mototsts and pedestrians will have time to either clear the crossing or come to a stop before entering the crossing. In most jurisdictions, the speed at which a trains can approach an automated crossing is strictly limited to ensure that the signals are active for at least a certain period of time before the train enters the crossing.
Existing automated rail way crossings, while a significant improvement over non automated crossings, suffer from several draw backs. In paticular, automated rail way crossings are triggered by either fast moving or slow moving trains. Since a slow moving train will necessarily take longer to enter a crossing than a faster moving train, the signal will be active for a relatively longer period of time. As a result, traffic is interrupted for a longer period of time. Also, existing crossings do not permit rail way corporations to adjust the time interval that the signal shall operate before the train enters the crossing, therefore, the operating time of the signal cannot be optimized for time of day or traffic conditions. There remains a need for an automated rail crossing which can adjust for train speed.